The present invention is related generally to detection of locked axle conditions and, in particular, to a method for verifying without a speed sensor the occurrence of an actual locked axle condition in a vehicle propelled by AC motors.
Locomotives used for hauling applications are generally equipped with speed sensors coupled to respective traction motors or to the axles driven by the motors. The speed sensor data or information may be used to detect a locked axle condition. If a locked axle condition occurs on a given axle while the locomotive is moving, the rotational speed of that axle decreases to zero, and all other axles rotate at a speed corresponding to the speed of the locomotive. Thus, a locked axle condition can be detected whenever a substantial difference in speed is sensed in one axle relative to the other axles.
In addition, when a speed sensor fails to supply reliable sensor data, a locked axle condition may be indicated in a system controller since existing controllers are not generally capable of detecting speed sensor failures. When a locked axle condition is indicated, the operator generally has to stop the train and visually inspect the axle or wheels for any discernable damage. If the visual inspection does not reveal any useful information, then the train may have to be rolled slightly to ascertain whether in fact the axle is locked or whether the condition was indicated due to a faulty speed sensor. If the latter is true, then the locomotive can be operated at lower speeds until the speed sensor and/or speed detection system can be repaired. Stopping trains, inspecting axles, and operating at lower speeds involve burdensome delays. Thus, there is a need for a low-cost method which will reliably distinguish between an actual locked axle condition and an erroneously detected axle condition, which may be indicated based on speed sensor failure.